Tetraalkylphosphonium fluoroalkylsulfonates are known to be prepared by reactions between sulfonyl derivatives and tetraalkylphosphonium halide derivatives in the presence of bases. These compounds are useful as antistatic agents in polymeric compositions, particularly in plastics such as PET (polyethylene terephthalate), PA (polyamide), PC (polycarbonate), polyketone and mixtures of butadiene-acrylonitrile-styrene. For their use as antistatic additives, these compounds are added to polymers either alone or in combination with other additives such as UV absorbers, flame retardants, light stabilizers, antioxidants, etc.
EP1462438 describes the preparation of tetrabutylphosphonium nonafluorobutane-1-sulfonate by combining an aqueous solution of tetrabutylphosphonium halide with an aqueous solution of (C4F9)-sulfonyl-O- M+, where M is a metal, to give a biphasic mixture which is separated and from which the bottom layer is recovered, preferably by solidification.
EP1737814 describes a process for the preparation of tetrabutylphosphonium nonafluorobutane-1-sulfonate which includes combining (C4F9)-sulfonyl-O- M+, where M is lithium or sodium, with tetrabutylphosphonium-halide in an aqueous solution.
EP182574 describes a process for the preparation of tetrabutylphosphonium nonafluorobutane-1-sulfonate which includes combining, in an aqueous solution, (C4F9)-sulfonyl-F with either tetrabutylphosphonium-OH or tetrabutylphosphonium-halide and a base selected from sodium hydroxide and lithium hydroxide.
WO2008108983 describes the reaction between potassium 1,1,2,3,3,3-esafluoropropanesulfonate and tetra-n-butylphosphonium bromide.
The above-mentioned procedures all involve the use of metals from which the desired compounds are difficult to be separated, thereby being very frequently contaminated therewith. The presence of metal traces in the tetraalkylphosphonium fluoroalkylsulfonate compounds leads to serious drawbacks. In fact, for their use as antistatic agents, the above-mentioned compounds should be highly purified because the presence of even a minimum of metal impurities leads to serious consequences in the preparation of plastic materials to which such compounds are added.